Differential Expression of Fungal Genes Determines the Lifestyle of Plectosphaerella Strains During Arabidopsis thaliana Colonization
Antonio Muñoz‐BarriosSara Sopeña‐TorresBrisa RamosGemma LópezIrene del HierroSandra Díaz-GonzálezPablo González‐MelendiHugo MélidaVanessa Fernández-CallejaVerónica MixãoMarina Martín‐DacalMarina Marcet‐HoubenToni GabaldónSoledad SacristánAntonio Molina
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Abstract:
The fungal genus Plectosphaerella comprises species and strains with different lifestyles on plants, such as P. cucumerina, which has served as model for the characterization of Arabidopsis thaliana basal and nonhost resistance to necrotrophic fungi. We have sequenced, annotated, and compared the genomes and transcriptomes of three Plectosphaerella strains with different lifestyles on A. thaliana, namely, PcBMM, a natural pathogen of wild-type plants (Col-0), Pc2127, a nonpathogenic strain on Col-0 but pathogenic on the immunocompromised cyp79B2 cyp79B3 mutant, and P0831, which was isolated from a natural population of A. thaliana and is shown here to be nonpathogenic and to grow epiphytically on Col-0 and cyp79B2 cyp79B3 plants. The genomes of these Plectosphaerella strains are very similar and do not differ in the number of genes with pathogenesis-related functions, with the exception of secreted carbohydrate-active enzymes (CAZymes), which are up to five times more abundant in the pathogenic strain PcBMM. Analysis of the fungal transcriptomes in inoculated Col-0 and cyp79B2 cyp79B3 plants at initial colonization stages confirm the key role of secreted CAZymes in the necrotrophic interaction, since PcBMM expresses more genes encoding secreted CAZymes than Pc2127 and P0831. We also show that P0831 epiphytic growth on A. thaliana involves the transcription of specific repertoires of fungal genes, which might be necessary for epiphytic growth adaptation. Overall, these results suggest that in-planta expression of specific sets of fungal genes at early stages of colonization determine the diverse lifestyles and pathogenicity of Plectosphaerella strains.Keywords:
Epiphyte
Host adaptation
The relationships between epiphytes and host specifity are known. We investigated the relation between specific epiphytes and tree fern trunks. Only some epiphytes are frequent or very frequent on tree ferns. Most of the epiphyte species are unspecific on these trunks. Blechnum fragile are the only found exclusively on tree ferns. We also observed different epiphyte communities dependent on the tree fern species and the morphology of the tree trunk.
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Polypodiaceae
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To explore the relationship among the rhizo-epiphyte, the endo-epiphyte and the plant, the present author takes as a sample the rhododerdron microphyton growing in Chuxiong, Yunnan Province and dissociates the rhizo-epiphyte from the endo-epiphyte in it.As a result, 75 epiphytes are obtained.Under the microscope, they are proved that they all fall into 8 genera of the same subordinate phylum, and of which, there are 31 penicillia, 41.3% of the total.The result shows the variety in the rhizo-epiphyte and endo-epiphyte of rhododerdron microphyton.
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Posidonia oceanica
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Facultative
Obligate
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Fog water is generally considered to be an important water source for epiphytes in cloud forests because they cannot directly access ground-level water sources. However, the water use proportions of potential water sources and water use efficiency of epiphytes in the subtropical montane cloud forests (MCF) remain to be further explored. In this study, we investigated the water use pattern in the dry season and the intrinsic water use efficiency (WUEi) of four epiphyte groups (i.e., epiphytic lichens, epiphytic bryophytes, epiphytic ferns, and epiphytic seed plants) using stable isotope (δ2H, δ18O, and δ13C) techniques. Our results indicated that the water sources of epiphytes were significantly different among groups and species. The contribution proportions of fog water to epiphytic lichens, epiphytic bryophytes, epiphytic ferns, and epiphytic seed plants were 83.2%, 32.7%, 38.8% and 63.7%, respectively. Epiphytic lichens and epiphytic seed plants mainly depended on fog water whereas the epiphytic bryophytes and epiphytic ferns relied on both fog water and humus. This may be due to their differences in morphological and structural traits (e.g., thallus or leaves, rhizoid or roots). Additionally, the difference in WUEi was also significant among epiphyte groups and species, which could be related to their different water acquisition patterns. In conclusion, our study reveals the differentiation of water utilization in epiphytes and confirms the importance of fog water for epiphytes during the dry season.
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Cloud forest
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Xishuangbanna is located at the northern margin of tropics. Its climate is different from that of typical tropics, but the rainforest there is not very different from that of the typical tropics in Southeast Asia. The main problems in Xishuangbanna are seasonal drought and low temperature. Fog may contribute to the development of rainforest here, but related studies are few. This study is aimed to know whether the leaves of epiphytes and non - epiphytes in Xishuangbanna can directly absorb fog water and contribute to their water status recovery, and whether epiphytes are more competent than non - epiphytes in their leaf fog water absorption. The study was conducted in dry season, and four species of epiphytes and six species of non - epiphytes were investigated. The effect of fog was imitated by spraying leaves with distilled water. For epiphytes and non - epiphytes, their leaf water potential (phi), relative water content (RWC), and amount of absorbed water increased gradually with the time of spraying, but the phi of epiphytes increased more quickly than that of non - epiphytes. The leaves of epiphytes Bolbitis scandens and Rhaphidophora decursiva could absorb fog water more quickly, and increase their RWC more greatly than those of non - epiphytes, indicating that these epiphytes were more competent than non - epiphytes in their leaf fog water absorption. The fog water absorption capacity of the leaves in epiphytic orchid Coelogyne occultata and Staurochilus dawsonianus was lower than that in Amischotolype hispida and Mananthus patentflora, but higher than that in other four non - epiphytes. The phi of epiphytes at early evening when no fog was formed was significantly lower than that at early morning, suggesting that fog water was absorbed by epiphytes at night to improve their leaf water status. Non - epiphytes did not need to absorb fog water directly through leaves, and they could recover their leaf water status through absorbing soil water by root system. Epiphytes except C. occultata had a much more leaf biomass than non - epiphytes, which was also beneficial to their leaf fog water absorption. Because there was abundant fog in dry season in Xishuangbanna, the phi of test ten species was higher than -0.8 MPa, indicating that water stress was not serious in dry season.
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We investigated the distribution of epiphytic macroalgae on the thalli of their hosts at eight localities along the southeastern coast of Cuba between June 2010 and March 2011. We divided he epiphytes in two groups according to their distribution on the host: those at the base of the thallus and those on its surface. We determining the dissimilarity between the zones and the species involved. We identified 102 taxa of epiphytic macroalgae. There were significant differences between the two zones. In 31 hosts, the number of epiphytes was higher on the surface of the thallus, whereas the number of epiphytes was higher at the thallus base in 25 hosts, and the epiphytes were equally distributed between the two zones in five hosts (R=−0.001, p=0.398). The mean dissimilarity between the two zones, in terms of the species composition of the epiphytic macroalgae, was 96.64%. Hydrolithon farinosum and Polysiphonia atlantica accounted for 43.76% of the dissimilarity. Among macroalgae, the structure of the thallus seems to be a determinant of their viability as hosts for epiphytes.
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Sargassum
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Epiphytes are a unique group of plants that live nonparasitically on other plants ("hosts") and constitute approximately one-fifth of Neotropical vascular plant diversity. However, the processes governing early epiphyte community assembly are poorly understood and have scarcely been experimentally tested. Here, we use an in situ experiment in the cloud forest of Santa Fé, Panama, to evaluate the extent to which host substrate texture regulates early epiphyte establishment. We experimentally varied the surface roughness of native wood substrates, applied bromeliad and orchid seeds to the substrates, and monitored emergence of epiphyte seedlings and their persistence for a year. Rougher substrates facilitated higher initial abundance of epiphyte seedlings; after two months, 81% of the 1,934 total germinated epiphytes occurred on the substrates with experimentally added roughness. Via photo analysis, we also show that epiphytes disproportionately established early on in the experimental grooves, wherein 71% more epiphytes per unit area occurred within 1.5 mm of the grooves than on nearby smooth surfaces. While epiphyte cohort survival rates differed between rough and smooth substrates in the first six months, more than 99% of all seedlings died after one year, regardless of experimental roughness treatment. Only 10 seedlings survived through the end of the experiment. Our results suggest that while substrate texture explains some variation in early epiphyte emergence, roughness alone is not sufficient to explain epiphyte persistence to adulthood. Moreover, our results highlight the importance of removal processes (e.g., wind, rain, animals) in structuring early epiphyte community assembly. Variation in substrate texture may contribute to differences in epiphyte diversity and community composition within- and among-host tree species, but more experiments are needed to disentangle removal processes from substrate-mediated host affinity.
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Cloud forest
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